This is called copyright infringement, and it is illegal.

If we are notified that a document you have uploaded to Scribd infringes someone else's copyright, we will take down the document immediately, as required by law, and we will notify you of the removal. If you persist in uploading unauthorized content, we will permanently ban your account and IP address from the Scribd, pursuant to our repeat infringer policy. 

Some important facts about copyright infringement:

• You can be sued for copyright infringement even if your account has been suspended.
• The length of a copied document does not matter, nor does the amount you may have copied: even a copying a small portion of a document may cause you to be liable for copyright infringement. See "Fair Use"
• A copyright notice (©) is generally not required for a work to be protected by copyright law.
• Distributing copyrighted content without the copyright owner’s permission is copyright infringement even if you give the document away for free.
• There is no exception for unauthorized copying and distribution for "private" use.  Even if you share a work with only a small group of your friends or family, you could still be liable for copyright infringement.
• There is no exception for the unauthorized copying and distribution of copyrighted content for educational or non-commercial use.
• You can be liable for copyright infringement even if you give attribution to the owner or author of the copyrighted content.
• Even if you used your creativity to make a new document that contained another person’s copyrighted work, you may be liable for copyright infringement.
• Even if there are documents on the Scribd site similar to the one you uploaded, you may be liable for copyright infringement if you upload an unauthorized document.

Content licensed with a Creative Commons license may be copied, distributed, and reused under certain circumstances. Read this article for more information.